So-called passive systems by means of which the sliding of a motor vehicle door is secured in the open position thereof after overcoming a mechanical resistance in order to prevent undesirable closure of the sliding door have already been known for a long time. To this end, there is used a mechanical door stop in the form of a locking latch which retains the door in the open position thereof. When the sliding door is intended to be closed again, the operator has to overcome the mechanical resistance in the opposite direction. For example, resiliently loaded stoppers are used as the resistance.
This known passive system is often uncomfortable for the operator since the resistance which is intended to be overcome requires a relatively large application of force. Therefore, there has already been developed a so-called active door stop (EP 1617031 A2 and EP 1717392 A2), in which the locking latch is released by means of an electromotive actuation device so that the sliding door can be readily pushed into the secured position thereof and back again.
Although this active system is comfortable to handle, it has the disadvantage that, for example, in the event of a power failure or a defect in the actuation device between the drive motor and locking latch, the sliding door is blocked in the open position thereof. An interruption of the blocking is possible only via a separate unlocking mechanism, which is complex to operate or which typically can be found only after searching through the operating instructions for the vehicle.